<div class="row">
  <div class="col-md-3">
    <button type="button" class="btn btn-primary" (click)="isCollapsed = !isCollapsed"
            [attr.aria-expanded]="!isCollapsed" aria-controls="collapseEvent">Toggle collapse
    </button>
  </div>
  <div class="col-md-9">
    <pre class="card card-block card-header">Event: {{message}}</pre>
  </div>
</div>
<hr>
<div id="collapseEvent" class="card card-block card-header"
     (collapsed)="collapsed()" (expanded)="expanded()" [collapse]="isCollapsed">
  <div class="well well-lg">Some content</div>
</div>
